The invention relates to a shut-off valve which comprises a valve housing having at least two mutually connecting chambers communicating with each other in each ease via a passage opening bounded by a valve seat surface and provided with ports for feed and discharge of a medium. Arranged in the valve housing is a valve body which is provided with at least one closing surface which can co-act with the valve seat surface. In a situation where the closing surface of the valve body is in sealing contact with the valve seat surface the connection between the chambers is closed and, when the valve body is moved such that the closing surface is released from the valve seat surface, the shut-off valve is opened.
Shut-off valves of this type are known wherein connecting to the valve seat surface or the closing surface is a slit-forming surface which forms with the opposite surface a slit extending all around in a practically closed position of the valve body. This slit-forming surface has at least one considerable axial directional component.
It can occur in such shut-off valves that the medium flowing through the slit causes resonances in the shut-off valve.
With the shut-off valve according to the present invention such resonances are prevented in a reliable manner. A stabilizing of the flow is achieved due to the notches which define a locally larger flow passage than the slit, so that no resonances occur.
The invention is particularly suitable in an embodiment wherein the valve seat surface or closing surface lying opposite the slit-forming surface is provided with at least one sealing ring of flexible material. Sealing rings of flexible material normally increase the susceptibility to resonance because they are compressed to a greater or lesser extent as a result of the pressure fluctuations occurring during resonance. Occurrence of resonances is also reliably prevented in this embodiment due to the notches.
The invention is particularly suitable for use in a shut-off valve of the leak detection type comprising a valve body with two parts movable relative to each other which each comprise a closing surface and between which debouches a leak detection channel leading outside the housing.
Such shut-off valves are applied particularly in the food processing industry where a possible leakage must be located immediately in order to prevent contamination of product liquids. Proper cleaning of the shut-off valve is herein essential to prevent growth of micro-organisms.
In such shut-off valves it is known to clean the leak detection channel simultaneously with one of the chambers by moving the valve body a short distance out of the closed position so that the cleaning liquid flows through the slit between the slit-forming surface and the oppositely located valve seat surface or closing surface. The cleaning liquid then flows to the outside via the leak detection channel.
In order to achieve good cleaning with a minimum quantity of washing liquid, which is desirable for environmental reasons, a small slit width is recommended.
However, in the known shut-off valves the stated resonance effect occurs to an extent which is progressively greater as the slit width decreases, so that in the shut-off valves of the prior art it is necessary to work with a considerable slit width. With the invention however, the slit width can be greatly reduced without the resonance effect occurring. Even when a sealing ring of flexible material is used and this sealing ring lies practically against the opposite surface, still no resonance occurs because possible pressure variations causing the resonance are equalized over this sealing ring immediately via the notches.
The invention will be further elucidated in the following description with reference to the embodiment shown in the figures.